The method of distinguishing between liquid samples on the base of the calculation of the initial moments of the intensity distribution number in their infrared spectra and the comparison of the obtained values with each other is proposed. The method allows to increase the sensitivity of spectroscopic study of liquid samples to the influence of low-intensity physicochemical factors, for example to the temperature change on units of degrees or to small changes in the concentration of solutes. In work the spectra of the following samples were considered: distilled water at -0,5±0,5 and –3,0±0,5°C, at –3,0±0,5 and –5,0±0,5°C and also at 25,0±0,5°C and tap water at 25,0±0,5°C. Moments were calculated for each water absorption band in the mid-IR region of the spectrum: the bending (1640 cm–1), combination (2090 cm–1) and stretching (3370 cm–1) bands. It was revealed that there is significant difference in the structure of distilled and tap water at 25,0±0,5°C. Also it was found that change in the structure of distilled water at the temperature transitions from - 0,5±0,5 to –3,0±0,5°C and from –3,0±0,5 to –5,0±0,5°C occurs by different mechanisms.